The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems may be used to perform etching, deposition, and/or other treatment of substrates such as semiconductor wafers. Example processes include, but are not limited to, chemical vapor deposition (CVD), atomic layer deposition (ALD), and/or other etch, deposition, and cleaning processes. A substrate may be arranged on a substrate support such as a pedestal, an electrostatic chuck (ESC), etc. in a processing chamber of the substrate processing system. Different gas mixtures including one or more precursors may be introduced into the processing chamber and plasma may be used to actuate chemical reactions.
The processing chamber typically includes a showerhead assembly, which is used to deliver the gas mixtures, and can be used as an electrical power conductor to the gas mixture. A showerhead assembly can include a stem with an internal channel through which the gases and precursors are supplied. The gases and precursors are received at a first end of the stem and provided to a showerhead at a second end of the stem. The showerhead can include a baffle plate, which is used to restrict, distribute and/or mix the gases and precursors within the showerhead. The electrical power applied to the showerhead can be used to generate plasma between the showerhead and the substrate support, or other aspects of the substrate processing system that require electrical power.
FIG. 1 shows a traditional baffle plate 10 and corresponding stem 12 and top plate 14 of a portion 16 of a showerhead assembly. The portion 16 is shown rotated 180°, such that the portion 16 is upside down. The showerhead assembly includes a showerhead that includes the top plate 14 and a bottom plate (may be referred to as a gas lens or faceplate). The bottom plate is not shown and extends below and parallel to the top plate 14. The stem 12 is cylindrically-shaped and includes an inner channel 22 for gases and precursors to pass to the showerhead plenum (or the space between the top and bottom plates). The baffle plate 10 is disc-shaped and can be perforated to include holes 24. The baffle plate 10 is held by standoff members 26 in a suspended position between an end 34 of the stem 12 and the bottom plate. The standoff members 26 extend from the stem 12 and/or the bottom plate in a direction parallel to a longitudinal center line (or axis) 28 of the stem 12 and are welded to the baffle plate 10. The end 34 of the stem 12 near the top plate 14 is welded to the top plate 14 to provide an inner stem weld 30. The inner stem weld 30 is circular and extends along and is attached to an inner circumferential surface 32 of the top plate 14 and the end 34 of the stem 12. Weld finishing and surface clean-up is performed to the baffle plate 10 subsequent to the welding of the standoff members 26.
Due to a low volume and flow rates of gases passing through ALD showerheads, baffle plates (e.g., the baffle plate 10) of the ALD showerheads tend to have a small diameter (e.g., less than 1.0 inches). This results in the standoff members having a diameter of, for example, 0.05 inches. Due to the small diameter of the standoff members, it can be difficult to weld the baffle plate to the standoff members. Also, due to the small size of the baffle plate, the welding of the baffle plate to the standoff members and cleanup of the welds can damage the baffle plate. The welding can warp the baffle plate and/or cause cracking near the holes of the baffle plate. Also, a surface of the baffle plate may be inadvertently damaged during grinding of the welds during cleanup, which can negatively affect the surface of the baffle plate. This can be due to slipped, uncontrolled and/or inaccurately controlled movement of tools during cleanup. The grinding can result in geometrical degradation of the baffle plate, the baffle plate having a course surface, and/or generation of particles that need to be removed. In addition, the welding of the baffle plate to the standoff members typically includes introduction of filler material, which can be susceptible to fluorine attack and degradation during use of the baffle plate.